How to install keyhole hangers

What is the proper way to install these keyhole picture hangers? If they are surface mounted, doesn't there have to be a hole or slot for

Fixing Materials Cabinet hanger, For mounting in drilled hole, keyhole slot

keyhole slot dimensions Wood Keyhole Slot Quilt Hangers ; Quantity: Out of Stock ; or call: 732-6304

keyhole slot bit Hillman Small Keyhole Hangers are used for hanging mirrors, paintings and more in a home or office space Made from a durable steel material